Mountains in the Snow, by Erich Heckel © akg-images/Artists Rights Society, New York City

Philippe Sands’s remarkable 2016 book, East West Street: On the Origins of “Genocide” and “Crimes Against Humanity,” weaves together the history of his family and that of two concepts central to his chosen profession as an international human-rights lawyer. All strands of that thought-provoking exploration run through the city now known as Lviv (formerly Lemberg and Lwów), where Sands’s Jewish forebears lived and were massacred during the Second World War, and where the two lawyers who conceived of the terms “genocide” and “crimes…